1. Field of the Invention
The present invention relates generally to a computer implemented method, data processing system, and computer program product for electronic design automation. More specifically, the present invention relates to placement of electronic objects or cells according to regional constraints.
2. Description of the Related Art
Physical design of integrated circuits has quickly progressed from a uniquely human endeavor to one that is human-directed but, to a large extent, machine-implemented. Design houses rely heavily on automated physical design tools to produce accurate, efficient designs in a small amount of time. Given a netlist description of an integrated circuit, the task of such tools is to place circuit modules on a layout of the integrated circuit and to route interconnections between the modules to achieve a compact layout without violating any design rules, which protect the functional integrity of the integrated circuit. Fully automatic layout systems for custom VLSI integrated circuits are used today. Examples of such systems (followed in parenthesis by the university at which they were developed) are the PI system (Massachusetts Institute of Technology), the Magic system (University of California at Berkeley), the Phoenix system (Stanford) and the Timberwolf system (University of California at Berkeley).
U.S. Pat. No. 5,308,798 (Brasen et al.) describes a circuit laid out as in computer memory having circuit entities interconnected between pins on the circuit entities. A set of pins to be interconnected forms a net and is assigned a weight. The method allows a user to cause the computer program for layout to place a circuit entity (or cell) at a different location on the integrated circuit layout than it would otherwise. Brasen defines a faked two-pin net as one pin being located on the circuit entity and another pin being located in a region of the integrated circuit in which the user desires the circuit to be placed.
The Brasen arrangement applies a bias or a weight to moving a cell or entity to a specific location or coordinate in the die where no existing pin exists to which it is to connect, nor for which a pin is likely to be placed. Moreover, Brasen continues to apply the bias regardless of the position of any intermediate placement of the cell.
Remedies are needed to help with placement and in particular pre-placement.